Hepatitis C (cont.)

Mary D. Nettleman, MD, MS, MACP

Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.

Jay W. Marks, MD

Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

What is hepatitis C infection?

Hepatitis C infection is an infection of the liver caused by the hepatitis C virus (HCV). It is difficult for the human immune system to eliminate HCV from the body, and infection with HCV usually becomes chronic. Over decades, chronic infection with HCV damages the liver and can cause liver failure. In the U.S., the number of new cases of HCV infection has declined from a peak of 200,000 annually to about 17,000 in 2007. When the virus first enters the body, however, there usually are no symptoms, so these numbers are estimates. Up to 85% of newly-infected people fail to eliminate the virus and become chronically infected. In the U.S., more than three million people are chronically infected with HCV. Infection is most commonly detected among people who are 40 to 60 years of age, reflecting the high rates of infection in the 1970s and 1980s. There are 8,000 to 10,000 deaths each year in the U.S. related to HCV infection. HCV infection is the leading cause of liver transplantation in the U.S and is a risk factor for
liver cancer.

What is the nature (biology) of the hepatitis C virus?

'Hepatitis' means inflammation of the liver. HCV is one of several viruses
that can cause hepatitis. It is unrelated to the other common hepatitis viruses
(for example,
hepatitis A or
hepatitis B). HCV is a member of the
Flaviviridae family of viruses. Other
members of this family of viruses include those that cause
yellow fever and
dengue.

Viruses belonging to this family all have
ribonucleic acid (RNA)
as their genetic material. All hepatitis C viruses are made up of an outer coat
(envelope) and contain enzymes and proteins that allow the virus to reproduce
within the cells of the body, in particular, the cells of the liver. Although
this basic structure is common to all hepatitis C viruses, there are at least
six distinctly different strains of the virus which have different genetic
profiles (genotypes). In the U. S., genotype 1 is the most
common form of HCV. Even within a single genotype there may be some variations
(genotype 1a and 1b, for example). Genotyping is important to guide treatment
because some viral
genotypes respond better to therapy than others. The genetic diversity of HCV is
one reason that it has been difficult to develop an effective vaccine since the
vaccine must protect against all genotypes.